This invention relates to mounting a sleeve on a central locating member by applying a preload to the locating member. The invention is advantageously used with bridge sleeves which are commonly used between a mandrel of a printing press and a print sleeve. More particularly, the invention relates to a clamping mechanism for mechanically clamping the bridge sleeve on a mandrel.
Although the invention will be explained in conjunction with a mandrel of a printing press, the invention is not limited to printing applications.
In printing machinery, the printing press often has a rotatable mandrel for carrying a cylindrical printing sleeve with the printing plate mounted to it. The press mandrel has a fixed diameter and is permanently mounted in the press. As the print repeat changes for various print jobs, the printing sleeve will have a changing wall thickness, sometimes becoming excessively thick. Thick print sleeve walls add undesirable handling weight and can be a source of loss of print system rigidity and printed image accuracy.
In order to overcome this problem, a cylindrical bridge sleeve has been added to some systems to bridge the annular gap between the fixed diameter press mandrel and the variable size print sleeve. The print sleeves have an oversized inside diameter to mate with the outside diameter of the bridge sleeve. The bridge sleeve is the topic of this patent.
In the present art, bridge sleeves are clamped to mandrels by compressing a sleeve liner on the mandrel, a tapered collet, or a split clamp collar. However, this art suffers from various problems. Compressing the print sleeve liner requires some kind of external energy supply, like pneumatic or hydraulic pressure, to either force the sleeve into contact with the mandrel or to release a prestressed sleeve liner from the mandrel. In some current implementations, a locking pin and notch is required on press mandrels, bridge sleeves, and print sleeves. These add expense, are prone to cause damage to sleeves, and do not provide sufficient radial rigidity to the bridge sleeve.
Tapered collets are hard to design and do not hold good concentricity between the print sleeve and the press mandrel.
Split clamps are inherently not concentric and usually require external tools and access to both ends of the sleeve.
All of the conventional designs are hard to assemble because they require close assembly clearance between the mandrel and the sleeve. They all have features that make them difficult to use. They demand special consideration in the press design, like hydraulic or pneumatic piping and controls, and/or they do not rigidly attach the sleeve to the mandrel concentrically.
To solve the foregoing problems, we invented a mechanical clamp system with a new approach to attaching the bridge sleeve to the mandrel. The mechanical clamp system does not use any of the standard approaches and requires no external tools or controls.
The invention uses the mechanical advantage of a small eccentric and the rigidity of a solid ring to clamp the bridge sleeve to the mandrel rigidly and concentrically up to the designed maximum external load when used with a close tolerance mandrel. All clamp actions can be actuated with a short finger lever on one end of the sleeve. When the clamp is released, the clearance between the sleeve and the mandrel is much greater than in standard designs in order to facilitate easy assembly of the sleeve on the mandrel.
A rigid ring is mounted inside each end of the bridge sleeve. The bores of the rigid rings have raised or radially inwardly extending fixed, accurate contact areas on one side designed to contact the mandrel. The contact area wraps less than 180 degrees around the mandrel. A clamp arm is mounted on each ring with a pivot on one end of the arm and an eccentric shaft extending through the other end. A raised or radially inwardly extending contact on the clamp arm is opposite the raised area on the ring. All raised areas and the eccentric are sized to conform the raised areas to the mandrel when the eccentric is in one extreme of travel and to provide a generous assembly clearance around the mandrel when the eccentric is in the other extreme of travel. The clamp arm is designed to have a narrow range of known spring rates when compressed against the mandrel by the eccentric. The forces on the clamp arm from the interference caused by the eccentric will be greater than all external loads on the bridge sleeve when the eccentric is moved to the point of maximum interference or just off from that point. Any other method of applying a controlled preload will also work. If the eccentric is rotatable slightly beyond the point of maximum interference, the eccentric is provided with an over center self-locking design. The design can include a cross shaft which connects the eccentric on one end of the bridge sleeve to the eccentric on the other end of the sleeve. In this way, both ends of the clamp mechanism can be actuated simultaneously while the user accesses only one end.